The present invention relates to a pellet formulation for the treatment of the intestinal tract, which comprises, as a pharmaceutical active compound, aminosalicylic acid or a pharmaceutically tolerable salt or derivatives thereof.
The active compound aminosalicylic acid (in particular 5-ASA) or its derivatives have been used successfully for a relatively long time for the treatment of intestinal disorders, such as, for example, ulcerative colitis and Crohn""s disease (DE 31 51 196 A1).
The use of 5-ASA and its derivatives as a chemotherapeutic agent in colonic cancer is likewise known, polyps in the colon and rectum being associated with an increased risk of carcinoma (WO 95/18622).
A coloscopic polypectomy in patients with polyps in the colon and/or rectum results in a considerable reduction in risk of the formation of colonic carcinomas and is recommended as a therapy, in particular in the case of colorectal polyps. The reccurrence rate after polypectomy, however, is high and amounts to about 6-30% per year. Aminosalicylic acid is suitable for the longer-term treatment of such patients and lowers the reccurrence rate of colorectal polyps.
The action of aminosalicylic acid in the treatment of intestinal disorders, or in the prevention of their recurrence or in the prevention of secondary disorders arising therefrom and possible accompanying disorders takes place by means of the contact of the active compound directly at the site of the disorder in the intestine, the action of the aminosalicylic acid, or a derivative thereof, being directly related to its local concentration in the intestinal area to be treated.
Since inflammatory processes often affect relatively large sections of the intestinal tract, the pharmaceutical form should spread reproducibly over wide areas of the intestine and release the active compound only at the site of inflammation.
A problem in the treatment with aminosalicylic acid is that the active compound is very easily absorbed and can be excreted via the kidney before its action can occur.
In the prior art, tablets and pellets are known which are coated with an enteric coating in order to thus prevent a premature release of the active compounds.
FR-A2 692 484 discloses a tablet for the controlled release of 4-ASA in a hydrophilic matrix which consists of swellable polymers forming a gel barrier, and having an enteric coating. After dissolution of the coating, the matrix swells and forms a gel barrier through which the active compound diffuses out. After an approximately two-hour lag phase, the composition disclosed in FR-A 2 692 484 releases the active compound approximately linearly in the intestine over a period of time of a further 14 h.
EP 0 453 001 A1 discloses a pharmaceutical composition in which the active compound is covered with at least two membranes, of which one is soluble at a pH of xe2x89xa75.5 and the other is insoluble at this pH but is permeable to the intestinal fluids.
EP 0 148 811 A1 discloses a pharmaceutical composition which consists of a core which contains the active compound. The core is surrounded by two layers, of which the inner layer is a diffusion membrane and the second layer is an anionic polymer and/or a fatty acid having a pKa of 4.5 to 7.
EP 0 629 398 A1 discloses pharmaceutical compositions in which the active compound-containing core is surrounded by an enteric phase. According to Example 2, the core can contain small amounts of hydroxypropyl-cellulose. The active compound should be released rapidly after dissolution of the enteric phase.
EP 0 485 840 A2 discloses an oral pharmaceutical form which contains a shell material surrounding the active compound consisting of a polysaccharide and a film-forming polymer material.
A disadvantage in the case of the pharmaceutical formulations known in the prior art is that the active compound is also absorbed into the blood circulation. This amount of active compound is thus lacking in the intestine, so that the effective dose of the medicament is reduced by the part of the active compound which is found in the blood.
Moreover, patients who suffer from intestinal disorders frequently have to be further treated over relatively long periods with the active compound, or derivatives thereof, after the acute disorder has died down in order to prevent the disorder flaring up again or secondary disorders resulting from the original disorder. In the case of such a long-term treatment, however, it has proven to be a problem that a certain nephrotoxicity of systemically available 5-ASA, i.e. 5-ASA found in the bloodstream, or derivatives thereof cannot be excluded (M. Barry, Prescribers Journal, 1992, 32, 205).
It is thus an object of the present invention to make available an orally administrable pharmaceutical formulation which does not have these disadvantages. According to the invention, formulations are therefore made available which have a controlled release profile which results in a high local active compound concentration at the site of action and simultaneously guarantees a blood level of the active compound which is as low as possible.
In the context of the present invention, it has now been found that pellet formulations are particularly suitable for this purpose, since unlike a tablet they spread the pharmaceutical form reproducibly over wide areas of the intestine and are thus particularly suitable for treatment of inflammatory processes, which often affect relatively large sections of the intestinal tract. In order to achieve the necessary local active compound concentration, the active compound must in this case be released at the site of inflammation within a relatively short time (up to a few hours) without, however, it being released virtually immediately, in order that its action does not wear off too rapidly.
The use of a swellable, gel-forming matrix such as described in FR-A 2 692 484 is not suitable for pellets having a diameter of xe2x89xa73 mm, since on account of the small diameter the polymer is very rapidly penetrated by the water, eroded as a result, and the active compound would thus be released virtually immediately (about 30 min).
In the context of the present invention, however, it has surprisingly been found that, if the active compound is present in the pellet core in a non gel-forming polymer matrix which is essentially insoluble and permeable to intestinal fluids and the active compound, a markedly reduced release of the active compound into the blood, with simultaneously increased local concentration of the active compound at the site of the disorder in the intestine, is guaranteed in comparison with aminosalicylic acid formulations already known in the prior art.
The present invention thus relates to an orally administrable pharmaceutical pellet formulation having a controlled release profile for the treatment of the intestinal tract, which comprises a core and an enteric coating, and, if appropriate, further pharmaceutically tolerable additives, the core including as a pharmaceutically active compound aminosalicylic acid or a pharmaceutically tolerable salt or derivative thereof, wherein the active compound is present in the core in a non gel-forming polymer matrix which is essentially insoluble in the intestinal tract and permeable to intestinal fluids and the active compound, the matrix-forming polymer making up at least 1% by weight of the total weight of the core.
The invention furthermore relates to a process for the production of the pellets described above and their use for the production of a medicament for the treatment of intestinal disorders, such as inflammatory intestinal disorders, preferably in the active phase and/or in the remission phase, for the prevention of these disorders, for the prevention of the recurrrence of these disorders or secondary disorders resulting therefrom, and of possible accompanying disorders and also for the treatment of intestinal cancer. The medicament is particularly suitable for the treatment of inflammatory intestinal disorders such as Crohn""s disease and ulcerative colitis, and for the prevention, treatment and/or prevention of the reformation of polyps in the gastrointestinal tract. Moreover, the medicament is suitable for the prevention of colorectal carcinomas in patients with adenomas and/or polypous growth, in particular with polypous growth in the intestine. The medicament is moreover used for lowering the recurrence rate of colorectal polyps.
Preferred active compounds are 5-aminosalicylic acid (also called mesalazine), 4-aminosalicylic acid and, serving as a prodrug for 5-ASA, 2-hydroxy-5-phenylazobenzoic acid derivatives such as sulfasalazine (5-[4-(2-pyridylsulfamoyl)phenylazo]salicylic acid) and balsalazide (the sodium salt of the azo derivative of 4-aminobenzoyl-xcex2-alanine and 5-aminosalicylic acid). 5-ASA is particularly preferred.
In addition to the active compound, the pellet core comprises 1% by weight, based on the total weight of the core, of a matrix-forming, non gel-forming polymer which is essentially insoluble in the intestinal tract and permeable to intestinal fluids and the active compound. Suitable matrix-forming polymers are, for example, those polymers which are known in the prior art as coating lacquers for delayed-release pharmaceuticals, such as, for example, (meth)acrylic ester copolymers.
Among the polymers which are essentially insoluble in the intestinal tract and permeable to intestinal fluids and the active compound, those are preferred which are insoluble or particularly preferably water-insoluble in the intestinal tract.
Methyl acrylate copolymers and ammoniometh-acrylate copolymers of the type such as can be obtained under the tradename Eudragit(copyright) RS/RL/NE are particularly preferred. As functional groups, these polymers have ester groups (Eudragit(copyright) NE) or ammonium groups (Eudragit(copyright) RL/RS). Poly(ethyl acrylate, methyl methacrylate) and poly(ethyl acrylate, methyl methacrylate, trimethylammonioethyl methacrylate chloride) are preferred. These polymers are obtainable, for example, as poly(ethyl acrylate, methyl methacrylate) 2:1 in 40% strength aqueous dispersion as Eudragit(copyright) NE 40 D and as poly(ethyl acrylate, methyl methacrylate, trimethylammonioethyl methacrylate chloride) 1:2:0.1 in 12.5% strength isopropanolic solution as Eudragit(copyright) RS 12.5 and in the composition 1:2:0.2 as Eudragit(copyright) RL 12.5. The most preferred is Eudragit(copyright) NE 40 D.
The polymer must be present in an amount which is sufficient to form a matrix for the active compound and which guarantees a delayed release of the active compound. For this purpose, an amount of at least 1% by weight, preferably at least 4% by weight, based on the total weight of the core, has proven suitable. Larger amounts of, for example, approximately 21% by weight can also be employed. 4% by weight to 10% by weight is preferably employed.
The active compound is preferably homogeneously dispersed in the matrix described above and is released with a delay after dissolving the enteric coating. The matrix with the active compound homogeneously dispersed therein advantageously extends through the entire core.
The enteric coating should only dissolve after the formulation has left the stomach. Necessary coatings for this purpose are disclosed in the prior art (e.g. EP 0 453 001 A1).
Preferred enteric coatings according to the invention comprise a methacrylic acid copolymer or methylhydroxypropylcellulose phthalate. Poly(meth-acrylic acid, methyl methacrylates), which are obtainable under the tradenames Eudragit(copyright) L or S and have free carboxyl groups as functional groups, are preferred. These polymers are insoluble in the gastric juice, but dissolve in digestive juices above pH 5.5-7 depending on the number of functional carboxyl groups. Poly(methacrylic acid, methyl methacrylate) 1:1 (Eudragit(copyright) L 100; methacrylic acid copolymer, USP/NF type A) and poly(methacrylic acid, methyl methacrylate) 1:2 (Eudragit(copyright) S; methacrylic acid copolymer, USP/NF type B) are particularly preferred. Eudragit(copyright) L 100 is the most preferred. Mixtures of the coating materials mentioned, in particular of Eudragit(copyright) L and Eudragit(copyright) S, can also be used.
The pellet formulation can comprise one or more coatings, however pellet formulations in which the pellet only comprises one coating are preferred.
Both the core and the coating of the pellet formulation according to the invention can include one or more of the abovementioned matrix or coating materials.
The pellet formulations according to the invention can additionally contain further pharmaceutically tolerable additives both in the core and in the coating. Examples of pharmaceutically tolerable additives include polyvinylpyrrolidone, microcrystalline cellulose, silica, magnesium stearate, lactose, cornstarch, triethyl citrate, talc, titanium dioxide and polyethylene glycol.
A particularly preferred pellet formulation according to the present invention comprises 5-ASA as an active compound in the core in a poly(ethyl acrylate, methyl methacrylate) 2:1 matrix, the polymer containing ester groups as functional groups, and an enteric coating which contains poly(methacrylic acid, methyl methacrylate) 1:1 or 1:2 with free carboxyl groups as functional groups, and, if appropriate, further pharmaceutically tolerable additives.
Moreover, a mixture of Eudragit(copyright) S and Eudragit(copyright) L, preferably approximately 1:1, is advantageously employed in a coating for the pellet formulations according to the invention.
The pellet formulation according to the invention is distinguished by a controlled release profile. Preferably, the release of active compound in 0.1 M HCl after 2 h is  less than 10%, in particular  less than 5%, and in artificial gastric juice at pH 6.8 after 0.5 h 10-30%, in particular 10-20%, after 2 h 40-60%, in particular 40-50%, and after 6 h at least 80%, in particular at least 85%.
The pellet formulations according to the invention can be prepared according to conventional processes known to the person skilled in the art. For example, the matrix material is first mixed with the active compound and, if appropriate, the further pharmaceutically tolerable additives and shaped to give pellets. The coating is then applied, e.g. sprayed on, in the form of a lacquer suspension in a suitable suspending agent such as ethanol and/or water. The pellets can in this case have a size of 0.1-3 mm, preferably 0.5-1 mm, and are combined in unit dose forms such as tablets or capsules for the production of a medicament. The present invention therefore also relates to pharmaceutical formulations which comprise the pellets according to the invention, in particular gelatin capsules which contain the pellets according to the invention.
On oral administration, the pellet formulations thus obtained result, in comparison with other preparations with the same active compound, in lower active compound concentrations in the blood with a simultaneously higher concentration of the active compounds in the intestine, as a result of which the side effect potential caused by the systemically available active compound or its metabolites, is markedly reduced.
The pellet formulation according to the invention is thus particularly suitable for the treatment of intestinal conditions in which a relatively long-term administration of the active compound is indicated, such as inflammatory intestinal disorders in their active phase and their remission phase, in the prevention of adenomas and/or polyp formation, in the prevention of the recurrence of adenomas and/or polyps and in the prevention of secondary disorders resulting therefrom and possible accompanying disorders.
FIGS. 1 and 2 show graphs of the plasma concentrations of 5-ASA (FIG. 1) and Ac-5-ASA (FIG. 2) against time.
The following examples serve to illustrate the invention.
Example 1 describes two different pellet cores (Example 1.1-1.2) and four different pellet coatings (Example 1.a-1.d). The different cores can be combined in any desired manner with the different coatings, the pellet core from Example 1.1 together with the coating from Example 1.a being a particularly preferred example.